Educational appliance



June 24, 1930.. I pgs cHsg 1,767,774

EDUCATIONAL APPLIANCES Filed Oct. 5, 19 25 Patented June 24, 1930 PATENT FECE HERMAN PAUL SACHSE, OF CHICAGO, ILLINOIS, ASSIGNOR T0 CENTRAL SCIENTIFIC COMPANY, OF CHICAGO, ILLINOIS, A CORPORATION OF ILLINOIS EDUCATIONAL APPLIANCE This invention relates to educational appliances, and particularly small apparatus including sheaves for changing the direction of motion of thread or cord (representing rope), and has for its principal objects to produce apparatus that will operate more smoothly, easily and quietly and give more accurate results; that will endure a longer period of service; that can be readily manufactured to a uniform standard, and that will make more of an appeal to students by its appearance than the apparatus now in use.

Further objects and advantages of the invention will be revealed as the disclosure proceeds and the descriptlon is read in connection with the accompanying drawings in which Fig. 1 is a perspective View of a pulley made according to the invention;

Fig. 2 is a perspective view of a triple sheave tackle block made according to the invention;

Fig. 3 is a similar view of the four-sheave tackle block, and

Fig. 4 is a transverse section of the tackle block shown in Fig. 1.

Referring now to the drawings, there is illustrated in Fig. 1 an embodiment of the invention which is by way of example only. As shown, the sheave block comprises a light shell made up of cheeks 22 which taper from the center outwardly, as indicated at 23, to points beyond the rim of the sheave 24, where they are provided with circular enlargements 25 that rest against spacer sleeves 26 and receive rivets 27 that serve to hold the cheeks together and form the shell. Beyond the enlargements 25 are reduced portions 28 terminating in similar enlarge- Inents 29 perforated to receive the hooks 30. In making shells for a larger number of sheaves, cheeks 22 are assembled with similar cheeks 122 that terminate at the enlargements 125 corresponding to the enlargements 25. Additional spacers 126 and 1 longer rivets 127 complete the equipment necessary to form a block such asillustrated in Fig. 3.

The sheaves 24 include a hub 31, a rim 82 provided with a gorge or groove 33, and a web 34 connecting the hub and rim. In the preferred construction the hub is longer than the thickness of the rim and the web is a relatively thin disk connecting the intermediate portions of the hub and rim. Also, in the preferred form the gorge is substantially V-shaped because in that way the cord can be certainly kept at the bottom of the gorge, and therefore it operates on the surface of an assumed diameter so necessaryto accurate results.

At the present time most of the apparatus in use includes sheaves made of two sheet metal halves riveted together. Even when new these sheaves lack uniformity and clevelop so much friction that the results demonstrated differ widely from the theoretical values, which, with the noisy operation and cheap appearance, engenders a disinterested and disrespectful attitude on the part of the students, greatly impairing the value of demonstrations. Moreover, the sheaves easily bend and corrode, the halves separate,

changing the effective diameters of the sheaves and eventually causing the cords to bind, the rough edges of the gorge outthe cord and have a tendency to foul the tackle.

The sheet metal halves are formed in dies that are costly to make and expensive to keep in repair. The formed halves are assembled by hand and riveted in a number of places. This assembly involves some error of alignment which is reflected in irregularities at the gorge and makes it necessary to drill the hole for the pin after the assembly is made. While the drill can be accurately centered by the use of a suitable jig, it tends to creep away and slight eccentricity is a uniform characteristic of these sheaves and this, of course, clearly affects the smoothness of operation and the accuracy of the results obtained with the tackle.

The assembled sheaves must be pickled and plated, or dipped and dried.

Altogether the manufacturing operations are so numerous that the cost of production is high and the manufacturing errors render uniformity in size and contour impossible.

Prior to the sheet metal construction heavy sheaves of cast brass or bronze Were used, but they had inherent disadvantages, both in operation and in the necessary process of manufacture, that rendered the sheet metal construction an improvement.

According to this invention the sheaves are made of bakelite by which it is intended to include that family of moldable gums produced with phenolic condensation and the imitations composed of shellac and the like with fillers known as mud.

Since sheaves can be made in one molding operation, and are delivered from the molds finished in their entirety, and ready for assembly in the shells, the molds are not more expensive than the dies used to form the sheet metal blanks, and their upkeep is negligible. The faces of the molds are smooth and even and the sheaves come out with a smooth surface presenting a finished and attractive appearance.

The bakelite sheaves can be made uniformly accurate to a standard size without any difficulty; they will run true throughout a long period of service; the bakelite hub on the metallic pin develops far less friction than the sheet metal or brass hub on the metallic pin, and they are lighter than any of the sheaves heretofore used, all of which contributes to greater accuracy in the results demonstrated and more close approach to the theoretical advantages that are intended to be taught.

The sheaves will not corrode and hence, will retain their uniform size and present a proper surface to the cords. Neither will they cut the cords, nor tend to foul the tackle. They are amply strong for the strains to be applied and will not warp either under the strains or under the effect of heat when stored in the school laboratories near radiators, or steam pipes, or the like; they will retain the attractive finished appearance throughout a long period of service; they will always operate smoothly and without noise.

The cost of production is very much less than the sheaves of the prior art.

Figs. 1, 2, and 3, illustrate only a few of many applications of apparatus involving sheaves and blocks made according to the invention.

I claim as my invention:

In an educational device a small, comparatively light pulley designed for educational purposes, said pulley comprising a relatively light sheave block, a sheave molded from bakelite and means for journaling said sheave in said block, said sheave comprising a wheel portion having a peripheral groove extending about the same and an integral hub portion extending laterally in opposite directions from, and axially of, said wheel portion, said wheel being substantially symmetrical with respect to the axis of said hub portions.

In testimony whereof I affix my signature.

HERMAN PAUL SAOHSE. 

